US20020099454A1 - Network-embedded device controller with local database - Google Patents

Abstract

A network-embedded device controller for industrial process control comprises a processor for running a real-time operating system, input devices measuring parameters related to an industrial process and operatively connected with the processor, an embedded service stack with a local database containing data related to the industrial process, and a dynamic service stack including a program executable by the processor to control the industrial process in a predetermined manner. The device has particular applicability for use with an in-motion weighing system.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0001]
• The present invention relates to industrial control devices and more particularly, to a network-embedded device for controlling industrial processes.[0002]
• 2. Background of the Invention[0003]
• Industrial processes typically are controlled by standard computers with serial interfaces to programmable logic controllers (PLC). The PLCs are configured to execute logic for controlling components of an industrial process line by sending appropriate control signals to system components via a communication connection. System components include line control relays, conveyors, sensors, solenoids and other devices collectively comprising the process machinery. The PLCs differ from standard PC-based computer controllers in that the PLC architecture is simpler and generally designed for a specific purpose and thereby more reliable than a PC-based controller.[0004]
• The simplified structure of PLCs, however, generally prohibits PLCs from interfacing with machines of different standards and protocols because each machine on an assembly line produces unique data, and may contain varying software platforms. Therefore, the scope of the control loop, the speed of the PLC and the interoperability of devices and machines controlled by the PLC are limited. Moreover, the PLC or PC-based controller typically obtains data for use in the decision making process from a database on the network, which slows down the overall speed of the system, and creates external dependencies.[0005]
• U.S. Pat. No. 6,061,603 purports to describe a system for remotely accessing an industrial control system over a commercial communications network. The control system allows a user to access a PLC system over a communications network using, for example, a web browser. The system includes an Internet web interface between the network and the PLC. The web interface serves web pages from an Ethernet interface on the PLC and includes a TCP/IP stack. With the interface, a user can retrieve pertinent data regarding operation of the PLC, including the PLC configuration, I/O and register status, operating statistics, diagnostics, and distributed I/O configurations. However, the system of the '603 patent has the disadvantage that no embedded local database system provides industrial process control information, so that fast, predictable control speeds are difficult to achieve.[0006]
SUMMARY OF THE INVENTION
• The present invention provides a network-embedded device controller (NEDC) for industrial process control, the NEDC including a processor for running a real-time operating system, input devices measuring parameters related to an industrial process and operatively connected with the processor, an embedded service stack with a local database containing data related to the industrial process, and a dynamic service stack including a program executable by the processor to control the industrial process in a predetermined manner.[0007]
• The present invention thus provides a system for controlling industrial processes with a remotely accessible NEDC comprising a real-time operating system for a central processing unit (CPU) for real-time execution of control application software to operate the process and calculate certain outputs as a function of a sensor input. The CPU is operably connected to the system components, which may include sensors, a local database, a central database, and a network interface. The term “realtime” as defined herein means response at specified machine times predictable within one millisecond.[0008]
• Information for the local database may be obtained during an initialization period via a network. The plurality of input devices may include a plurality of sensors, including a local sensor set and a global sensor. The sensors can measure pertinent system data such as machine states and external variables, e.g., roll, pitch, yaw, horizontal oscillations and vertical oscillations. One of the input devices also may be a PLC.[0009]
• The controller preferably is connected to an input sensor through a network switch.[0010]
• Preferably, the program run by the NEDC may control a device as a function of the local database and as a function of the information from the input sensor.[0011]
• The NEDC has particular applicability as a controller for an in-motion weighing system, with the controller determining a weight of an object. The input devices of the system include a scale, a local sensor array, global sensor and local database.[0012]
• The present invention also provides a method of controlling an industrial process comprising the steps of:[0013]
• loading database information onto a local database of an embedded service stack of a network-embedded device controller;[0014]
• receiving input data of the industrial process at the network-embedded device controller; and[0015]
• performing an industrial process calculation at the network-embedded device controller as a function of information in the local database and the input data.[0016]
• The method may further include scanning an object so as to form part of the input data.[0017]
• Preferably, the receiving input data step may include receiving data from a PLC.[0018]
• The industrial process calculation may include calculating a weight of an object.[0019]
• The present invention also provides an in-motion weighing system having a spacing conveyor for transporting objects to be weighed, a scale conveyor receiving the objects from the spacing conveyor, and a network-embedded device controller having a processor, an dynamic service stack containing a real-time executable program for controlling the spacing conveyor and determining a weight of the objects, and an embedded service stack containing a local database having information related to the objects to be weighed.[0020]
• A local sensor set permits determination by the program of accelerations affecting the objects to be weighed while a global sensor provides an input to the controller.[0021]
• A scanner may scan the objects prior to the spacing conveyor so as to permit the NEDC to accept random introduction of objects defined in the local database and determine the proper spacing and throughput rate for same.[0022]
• A bar code label printer may print bar code labels to be attached to the objects, the labels detailing the identity and the weight of the object.[0023]
• The NEDC of the present invention may be implemented as a stand-alone system or added onto an existing programmable logic controller. The system provides useful embedded services such as a real-time operating system, local databases and a common computing platform for applications requiring millisecond response times for complex algorithms functioning on input from local and remote, networked sensors.[0024]
• It should be noted that the present invention may be implemented in any type of industrial process where independent real-time processing of manufacturing information is needed. However, in a preferred embodiment, the NEDC assesses the weight of items moving along a conveyor belt. Fast and accurate resolution of gravity on objects accelerated through a system is accomplished by uncoupling forces other than gravity acting on the object by real-time integration of motion detection and strain gauge data. The process involves sampling object motions through a particular field and integrating the resultant forces. Specific examples include an NEDC-enabled weighing system operating in unstable environments, such as a fishing ship at sea where both the object to be weighed and the weighing system are unstable, subjected to forces pushing and pulling in all directions. Another type of example exists where the object is moving but the system is stationery. For example, weight stations for vehicles moving at highway speeds, or products passing through a production process. In all cases, objects are subject to forces spatially interacting with gravity, e.g., vertical oscillations. These forces are isolated by the NEDC with high sampling rates of weight measurement, object movement by measuring disturbances in a field projected by a local sensor array, and system movement with respect to the earth's gravitational field.[0025]
• Referring to the fishing boat example, the pitching and rolling of the ship produces forces on the weighing system and the objects passing through the system. Sensors detect and measure motions of the ship, the system, and the objects. The measured forces are resolved with respect to the earth's gravitational field to obtain an acceleration-referenced weight measurement by digitally separating all forces acting on the object, except for gravity.[0026]
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be further elucidated with reference to a particular weighing system embodiment of the present invention in which:[0027]
• FIG. 1 shows a block diagram of an network embedded device controller according to the present invention.[0028]
• FIG. 2 shows an in motion weighing system according to the present invention.[0029]
• FIG. 3 shows the service stacks of FIG. 1 in detail.[0030]
• FIG. 4 shows a flowchart detailing the process of the system in FIG. 2.[0031]
DETAILED DESCRIPTION
• FIG. 1 shows a block diagram of an NEDC according to the present invention. An[0032]NEDC10 contains aCPU13, adynamic service stack14, an embeddedservice stack12, amemory module17, an I/O controller16, and anetwork interface18. The components of theNEDC10 are connected via acenterplane15. TheNEDC10 communicates withremote users25, a centraldatabase web server24 for controlling thedynamic service stack14, and apeer device controller37 via acommunication network23 through a network switch21 and afirewall22. TheCPU13 manages system components to execute specific functions in a prescribed sequence and obtain the data necessary to control an industrial process.
• While the[0033]NEDC10 can process all control commands with software on the dynamic service stack, it also can interact with aPLC19, if desired, through I/O device16. Thus thePLC19 can, if present, provide specific preliminary control functions for a specific sensor ordevice32. TheNEDC10 of the present invention thus can operate in conjunction with existing PLC devices, such as the PLC of U.S. Pat. No. 6,061,603, which is hereby incorporated by reference herein.
• System operators may access the[0034]NEDC10 from within the local network through the network switch21 or aremote user25 can gain access across thecommunications network23 via thefirewall22. A central web-server anddatabase24 controls and updates the dynamic and embeddedservice stack14, which is responsible for executing the control logic.
• [0035]Remote users25 can directly access thedevice controller10 to set local parameters stored in the database of the embeddedservice stack12 and to load an application program intodynamic service stack14. These parameters are necessary to execute the control logic independent of the centraldatabase web server24.
• The local database is located in the embedded[0036]service stack12 and stores operative configuration data, such as requirements, for example quality requirements, and parameters. Thecentral database24 provides this information to the local database during an initialization period. The operation of theNEDC10 will be described in more detail with respect to FIG. 4.
• FIG. 2 shows an in-motion weighing system according to the present invention.[0037]NEDC10 is operably connected to an I/O controller42 and a network switch58. The I/O controller42 interfaces with a spacing conveyor54, alocal sensor array52, scale or weighing conveyor50, a bar-code label printer48, anaudit scanner46, and a global sensor64. Products to be weighed enter spacing conveyor54 via anapproach conveyor70. Spacing conveyor54 sets the weighing process speed and the spacing between products to be weighed. Scale conveyor50 is a conveyor with a strain gauge for measuring the force of an object on the conveyor50. The object to be weighed is then transported further by a take-awayconveyor44.
• The network switch[0038]58 provides connectivity to a communication network, such as a global communication network such as theInternet62, via a firewall60. In addition, switch58 is connected to an ID scanner56, which can be used to identify the products to be weighed.
• The global sensor[0039]64 is an external sensor outside the local environment, and senses forces global tolocal sensor array52, which consists of a number of sensors that project a field in which objects to be weighed are tracked in three dimensions. For example, global sensors64 could sense whole ship movements, whilelocal sensors52 sense movements of a fish on the conveyor. Therefore, global sensor64 provides a reference point from which to determine the forces acting on the weighing system and the object to be weighed. Global sensor64 may itself be an NEDC performing necessary measurements. Readings from the global sensor64 and thelocal sensors52 are processed to evaluate the accelerations that the system and object to be weighed are subject to. Where the system is stationary, the global sensor64 may not be necessary.
• FIG. 3 shows the NEDC service stacks[0040]12,14 in more detail.Dynamic service stack14 is controlled by thenetwork database server24 and is updated via FTP or COBRA protocol according to an application program that resides on thedatabase server24. The embedded services in embeddedservice stack12 reside locally and independently of thenetwork database server24.
• The system operates according to the application program of the[0041]dynamic service stack14 and data stored in the local database11 of the embeddedservice stack12. Operating parameters registered by a remote user set the operating parameters for theNEDC10 to function as a standalone unit for the time necessary to maintain a maximum amount of up-time and for fault tolerance with respect to thecommunication network23 and central database web-server24.
• Now referring to FIG. 4, there is shown a flowchart for the process of the system in FIG. 2. The parameters for operating the system are set (step[0042]402) by a user communicating with the CPU over the network. For example, if fish on a boat are to be weighed, the local database is loaded with information relating fish size to an approximate weight. Thus fish between3 inches long and6 feet long, for example, are provided with approximate weights. This information is stored locally in he NEDC10 at database11. The information then is not again called from thecentral database24 during the weighing operation. In thedynamic service stack14, an application program for weighing fish on a boat also is loaded. The application program provides the logic for determining how to weight the fish, given that the ship is in motion and the fish as well is moving. Accelerations not related to the fish weight are filtered out by the application program. The various inputs from the sensors are thus used to modify a strain gauge reading on the scale conveyor50 to obtain the actual fish weight. A margin of error for the weighing can also be stored in local database. The margin of error can be used by the application program to set the spacing of spacing conveyor54 and the speed with which the fish are processed. The longer the fish remains on scale conveyor50, the more accurate the weight reading.
• The object to be weighed enters the system on the[0043]approach conveyor70 where it is scanned by the ID scanner56 (step404). For example the fish length is approximated. The scanning information is sent to the NEDC10 (step406) for identification of the object and retrieval of system configuration information based on the object particulars (step408) such as estimated mass, over/under weight tolerances, tare weight of any packaging, product profile and specific accuracy requirements from the local database of the embedded service stack. For example, the local database may contain information indicating that a fish three feet long should weigh approximately fifty pounds. In addition, the local database may contain information required to build customer-specific orders for subsequent resynchronization with the central database.
• The system then determines the appropriate speed of the spacing conveyor, as a function of the particulars from the local database information (step[0044]410) and any relevant global variables, such as the pitch and yaw of the ship. For example, for fish of about fifty pounds, the fish should remain at least 1.4 seconds (or another time) on the scale conveyor so as to obtain the desired accuracy. Also, in smooth seas, for example, the spacing conveyor may operate at higher speeds while still achieving a desired accuracy. With the present invention, these calculations all take place real-time with the NEDC: no outside database access is required. Next, a signal is sent to the appropriate system components to set appropriate conveyor speeds (step412). In the system of FIG. 2, the appropriate components include the spacing conveyor54 and the scale conveyor50. The product66 then enters the spacing conveyor54 for proper space registration onto the scale conveyor50. For example, fish of about three feet (about 50 lbs) should be spaced a certain space apart so that the desired time on the scale conveyor is achieved.
• As the product[0045]66 passes across the scale conveyor50, alocal sensor array52 connected through the I/O controller42 collects raw data relating to movement of the5 product68 on the scale conveyor (step414). This raw data is then integrated with data from the global sensor64 and the strain gauge of the scale conveyor50 and processed by the application program (step416) to digitally uncouple all accelerations other than gravity for the weight calculation (step418). Output weight and other relevant data is then relayed to the bar-code printer48 (step420) for application of a Io bar-code label on the product66. The bar code label is then verified by an audit scanner46 (step422). The embeddeddatabase client services16 allow for the periodic resynchronization of the local database1 with the central database24 (step424).
• The[0046]NEDC10 of the present invention permits real-time control of the15 weighing process so as to permit accuracies and stability not known to be achievable with a traditional PLC or PC-based controller.

Claims (21)

What is claimed is:

1. A network-embedded device controller for industrial process control comprising:

a processor for running a real-time operating system;

input devices measuring parameters related to an industrial process and operatively connected with the processor;

an embedded service stack with a local database containing data related to the industrial process; and

a dynamic service stack including a program executable by the processor to control the industrial process in a predetermined manner.

2. The controller as recited inclaim 1 wherein information for the local database is obtained during an initialization period via a network.

3. The controller as recited inclaim 1 wherein the plurality of input devices includes a plurality of sensors.

4. The controller as recited inclaim 3 wherein the plurality of sensors includes a local sensor set and a global sensor.

5. The controller as recited inclaim 1 wherein the parameters include a machine state and variable external to the controller.

6. The controller as recited inclaim 1 wherein the parameters include roll, pitch, yaw, horizontal oscillations and vertical oscillations.

7. The controller as recited inclaim 1 wherein one of the input devices is a PLC.

8. The controller as recited inclaim 1 wherein the controller is connected to an input scanner through a network switch.

9. The controller as recited inclaim 8 wherein the program is further executable to:

control a device as a function of the local database and as a function of the information from the input scanner.

10. The controller as recited inclaim 1 wherein the controller is a controller for an inmotion weighing system.

11. The controller as recited inclaim 1 wherein the controller determines a weight of an object.

12. The controller as recited inclaim 11 wherein the input devices include a scale, a local sensor array and a global sensor.

13. A method of controlling an industrial process comprising the steps of:

loading database information onto a local database of an embedded service stack of a network-embedded device controller;

receiving input data of the industrial process at the network-embedded device controller; and

performing an industrial process calculation at the network-embedded device controller as a function of information in the local database and the input data; and

synchronization of the local database with a central database.

14. The method as recited inclaim 13 further comprising scanning an object so as to form part of the input data.

15. The method as recited inclaim 13 wherein the receiving input data step includes receiving data from a PLC.

16. The method as recited inclaim 13 wherein the industrial process calculation includes calculating a weight of an object.

17. An in-motion weighing system comprising:

a spacing conveyor for transporting objects to be weighed;

a scale conveyor receiving the objects from the spacing conveyor; and

a network-embedded device controller having a processor, an dynamic service stack containing a real-time executable program for controlling the spacing conveyor and determining a weight of the objects, and an embedded service stack containing a local database having information related to the objects to be weighed.

18. The system as recited inclaim 17 further comprising a local sensor set for permitting determination by the program of accelerations affecting the objects to be weighed.

19. The system as recited inclaim 18 further comprising a global sensor for providing an input to the controller.

20. The system as recited inclaim 17 further comprising a scanner for identifying the objects prior to the spacing conveyor.

21. The system as recited inclaim 17 further comprising a bar code label printer for printing bar code labels detailing an identity and the weight of the object.

Images